 
 (defmethod extract-access-value "application/echo10+xml"
   [concept]
-  (when-let [[_ restriction-flag-str] (re-matches #"(?s).*<RestrictionFlag>(.+)</RestrictionFlag>.*"
-                                                  (:metadata concept))]
-    (Double. ^String restriction-flag-str)))
+  (let [^String metadata (:metadata concept)]
+    ;; This contains check is a performance enhancement. This saves a lot of time versus the regular
+    ;; expression below when the metadata is a large string.
+    (when (.contains metadata "Restriction")
+      (when-let [[_ restriction-flag-str] (re-matches #"(?s).*<RestrictionFlag>(.+)</RestrictionFlag>.*"
+                                                      metadata)]
+        (Double. ^String restriction-flag-str)))))
 
 (defmethod extract-access-value "application/dif+xml"
   [concept]

            "tombstone-filter time:" t3
            "concept->value-map time:" t4)
     values)))

  (info "Transforming" (count concepts-tuples) "concept(s) to" format)
  (let [mdb-context (context->metadata-db-context context)
        [t1 concepts] (u/time-execution
                        (doall (metadata-db/get-concepts mdb-context concepts-tuples allow-missing?)))
        [t2 values] (u/time-execution
                      (doall (pmap #(concept->value-map context % format) concepts)))]
    (debug "get-concept-revisions time:" t1
